We report astrometric results of phase-referencing VLBI observations of 43 GHz SiO maser emission toward the red hypergiant VY Canis Majoris ( VY CMa ) using the Very Long Baseline Array ( VLBA ) .
We measured a trigonometric parallax of 0.83 \pm 0.08 mas , corresponding to a distance of 1.20 ^ { +0.13 } _ { -0.10 } kpc .
Compared to previous studies , the spatial distribution of SiO masers has changed dramatically , while its total extent remains similar .
The internal motions of the maser spots are up to 1.4 mas yr ^ { -1 } , corresponding to 8 km s ^ { -1 } , and show a tendency for expansion .
After modeling the expansion of maser spots , we derived an absolute proper motion for the central star of \mu _ { x } = -2.8 \pm 0.2 and \mu _ { y } = 2.6 \pm 0.2 mas yr ^ { -1 } eastward and northward , respectively .
Based on the maser distribution from the VLBA observations , and the relative position between the radio photosphere and the SiO maser emission at 43 GHz from the complementary Very Large Array ( VLA ) observations , we estimate the absolute position of VY CMa at mean epoch 2006.53 to be \alpha _ { J 2000 } = 07 ^ { h } 22 ^ { m } 58 { \hbox to 0.0 pt { . } } ^ { s } 3259 \pm 0 { \hbox to 0.0 pt { . } } ^ { s } 0007 , \delta _ { J 2000 } = - 25°46′03 { \hbox to 0.0 pt { . } } { { } ^ { \prime \prime } } 063 \pm 0 { \hbox to 0.0 pt { . } } { { } ^ { \prime \prime } } 010 .
The position and proper motion of VY CMa from the VLBA observations differ significantly with values measured by the Hipparcos satellite .
These discrepancies are most likely associated with inhomogeneities and dust scattering the optical light in the circumstellar envelope .
The absolute proper motion measured with VLBA suggests that VY CMa may be drifting out of the giant molecular cloud to the east of it .